how to weight x25

How are you guys weighting the x25. My buddy got a new one and last week we were using factory ballast and 10 adults. Wake was big but super inconsistent and washy at times. When it was clean it was great. This week we will try placing some bags but had trouble getting on plane with last weeks load. We added two more people and the boat would not plane out at all even when we dropped some ballast from the back and added more people to the front. I think something is wrong with it as adding 350 lbs in the front shouldn't have killed it since it got on plane fine earlier in the day. It has the stock prop and we are going to change to his power prop, but want to make sure nothing is wrong with the boat first. The engine is the ilmor 6.0